1. Field of the Invention
The invention relates a system and method of equipping specific types of nuclear power plants with low cost storage that has a very high thermal efficiency.
The invention also relates to systems and methods for operating nuclear reactors cost-effectively at maximum capacity so that nuclear plants will be able to compete with conventional fossil fueled power plants in their responsiveness to load changes over a wide range.
The invention also relates to a storage system and method for a high-temperature gas-cooled nuclear reactor wherein the storage system or the method has a high efficiency (over 90%) and a low cost, allowing the nuclear reactor to always operate at maximum reactor power, while remaining capable of varying its electrical output as does a steam power plant.
2. Discussion of Background Information
Nuclear reactors have a large thermal inertia, which slows their responsiveness to variations in the demand for power from the grid. Their potential to become the major source of electricity is seriously affected by this limitation. Additionally, the initial cost of investment in a nuclear power plant is high; therefore, they must be built to operate at full capacity as it is too costly to operate them at low loads. Commercial nuclear reactors are kept operating full time to ensure a profitable return on the original investment, therefore, most nuclear reactors are designed for base load. Operating them at or below half-capacity is not economically attractive since halving the load nearly doubles the cost per KWh. Another limitation on their functionality is that due to their thermal inertia, nuclear reactors can have a slow transient response.
As currently designed, nuclear power plants are unable to follow the variable demands of the grid because they are expensive to operate at intermediate loads and unsuitable for rapid load following. Because they are used mostly for base power, the total contribution they can make to the grid is thereby limited. Sixty percent of the demand for electricity is for variable, controllable power. At present, this need is supplied by coal-fired steam and gas turbine power plants and to some extent by hydroelectric power. While coal-fired steam power plants can respond to load changes quickly and can operate well with a load of only 13% of design capacity, they are more expensive to use for generating electricity during periods of partial load as they must be designed for maximum capacity.
Various energy storage devices have been proposed to solve this problem, but all of these proposals have limited efficiency (about 75%) and are expensive. Furthermore, while storage systems have been proposed for solar thermal power plants (see Sargent & Lundy, “Assessment of Parabolic Trough and Power Tower Solar Technology Cost and Performance Forecasts”, SL-5641, (2002), the disclosure of which is hereby expressly incorporated by reference in its entirety), they are based on liquid heat transfer fluids and molten salts, which may be unsuitable for nuclear reactors. The system described therein uses hundreds to thousands of sun-tracking mirrors called heliostats to reflect the incident sunlight onto the receiver. These plants are best suited for utility-scale applications in the 30- to 400-MWe ranges. In a molten-salt solar power tower, liquid salt at 290° C. (554° F.) is pumped from a “cold” storage tank through the receiver where it is heated to 565° C. (1,049° F.) and then on to a “hot” tank for storage. When power is needed from the plant, hot salt is pumped to a steam generating system that produces superheated steam for a conventional Rankine-cycle turbine/generator system.
Consider, for example, a high temperature nuclear reactor cooled by helium (He) or any intermediate heat transfer medium (see Baxi, C. B., et al.; “Evolution of the Power Conversion Unit Design of the GT-MHR”, presented at the International Congress on Advances in Nuclear Power Plants, (2006), the website the entry for Pebble Bed Reactor on Wikipedia and Penner, S, S.; Seiser, R. Schultz, K.; “Nuclear Energy for the Future”, Presented at the Meeting of the Doctors for Disaster Preparedness, Las Vegas Nev., 16-17 Jul. 2005, the disclosures of which are hereby expressly incorporated by reference in their entireties).
The invention solves one or more of the problems associated with conventional nuclear power plants, is simple in design, is more robust, is cheaper and lacks one or more of the disadvantages of conventional nuclear power plants.